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United States Patent |
5,781,986
|
Maurice
,   et al.
|
July 21, 1998
|
Method of making a magnetic recording/reading head
Abstract
A method for the making of a magnetic recording/reading head comprises the
following steps:
the making of magnetic excitation wires on or in a first face of a
substrate having this first face and a second face opposite the first
face;
the making, on the first or second face of the substrate, of at least two
magnetic poles separated by a gap;
the drilling of holes through the substrate from the face opposite the one
bearing the magnetic poles, each ending in such a way that there is
magnetic coupling between the bottom of the hole and the pole;
the deposition of a layer of material with high magnetic permeability in
the holes and in the zones of the substrate located between the holes.
Applications: the making of magnetic recording/reading heads for
video-tape recorders, computer peripherals and professional recording
machines.
Inventors:
|
Maurice; Fran.cedilla.ois (Verrieres le Buisson, FR);
Coutellier; Jean-Marc (Maurepas, FR);
Pirot; Fran.cedilla.ois-Xavier (Magny, FR)
|
Assignee:
|
Thomson-CSF (Paris, FR);
Thomson Multimedia (Courbevoie, FR)
|
Appl. No.:
|
560384 |
Filed:
|
November 17, 1995 |
Foreign Application Priority Data
Current U.S. Class: |
29/603.14; 29/603.25; 29/603.26 |
Intern'l Class: |
G11B 005/42 |
Field of Search: |
29/603.13,603.14,603.15,603.25,603.26
|
References Cited
U.S. Patent Documents
3564522 | Feb., 1971 | Stevens, Jr.
| |
3672043 | Jun., 1972 | Trimble et al.
| |
4477853 | Oct., 1984 | Lemke.
| |
4731157 | Mar., 1988 | Lazzari | 29/603.
|
5042140 | Aug., 1991 | Coutellier et al.
| |
5067230 | Nov., 1991 | Meunier et al.
| |
Foreign Patent Documents |
0 032 230 | Jul., 1981 | EP.
| |
0 269 489 | Jun., 1988 | EP.
| |
0 406 052 A1 | Jan., 1991 | EP.
| |
0 463 908 | Jan., 1992 | EP.
| |
1952402 | Apr., 1971 | DE.
| |
WO 90/07772 | Jul., 1990 | WO.
| |
WO 92/14250 | Aug., 1992 | WO.
| |
Primary Examiner: Hall; Carl E.
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier & Neustadt, P.C.
Claims
What is claimed is:
1. A method for making a magnetic recording/reading head comprising the
steps of:
providing a substrate having a first face and a second face;
providing magnetic excitation wires on the first face of said substrate;
providing an insulation layer on said wires;
forming, on the insulation layer, at least two magnetic poles separated by
a gap;
drilling holes through the substrate and the insulation layer from the
second face of the substrate; and
depositing a layer of material with high magnetic permeability in the holes
for the purpose of establishing magnetic coupling between the poles.
2. A method according to claim 1, further comprising the step of bonding
the second face of the substrate to a supporting plate.
3. A method according to claim 1, wherein the step of providing the
magnetic poles further comprises the steps of:
providing a first magnetic pole on the insulation layer, said first pole
having an edge;
providing a layer of non-magnetic material having a thickness smaller than
that of the first magnetic pole on the edge of said first pole and on the
insulation layer;
providing a second pole on said non-magnetic layer; and
machining said second pole and the non-magnetic material located on the
edge of said first pole.
4. A method according to claim 1, wherein electronic control circuits are
made on or in the first face of said substrate.
5. A method according to claim 4, wherein the substrate is a semiconductor
material and wherein the electronic circuits are implanted in the
substrate.
6. A method according to claim 1, wherein the material with high magnetic
permeability is permalloy.
7. A method according to claim 1, wherein the step of providing the
magnetic poles further comprises the steps of:
providing an intermediate plate having a first face and a second face;
providing at least two magnetic poles separated by a gap on the first face
of said intermediate plate; and
bonding the second face of the intermediate plate to said insulation layer.
8. A method according to claim 7, wherein the intermediate plate is made of
non-magnetic material.
9. A method according to claim 7, wherein the intermediate plate is made of
a composite material of magnetic elements and non-magnetic elements
perpendicular to said first and second faces, the magnetic elements
magnetically coupling each pole to the second face of the intermediate
plate.
10. A method for making a magnetic recording/reading head comprising the
steps of:
providing a substrate having a first face and a second face;
providing magnetic excitation wires on the second face of said substrate;
providing an insulation layer on said wires;
forming, on the first face of said substrate, at least two magnetic poles
separated by a gap;
drilling holes through the substrate and the insulation layer from the
second face of the substrate; and
depositing a layer of material with high magnetic permeability in the holes
for the purpose of establishing magnetic coupling between the poles.
11. A method according to claim 10, further comprising the step of bonding
the insulation layer to a supporting plate.
12. A method according to claim 10, wherein the step of providing the
magnetic poles further comprises the steps of:
providing a first magnetic pole on the first face of said substrate, said
first pole having an edge;
providing a layer of non-magnetic material having a thickness smaller than
that of the first magnetic pole on the edge of said first pole and on the
first face of said substrate;
providing a second pole on said non-magnetic layer and on the first face of
said substrate; and
machining said second pole and the non-magnetic material located on the
edge of said first pole.
13. A method according to claim 10, wherein electronic control circuits are
made on or in the second face of said substrate.
14. A method according to claim 13, wherein the substrate is a
semiconductor material and wherein the electronic circuits are implanted
in the substrate.
15. A method according to claim 10, wherein the material with high magnetic
permeability is permalloy.
Description
BACKGROUND OF THE INVENTION
The invention relates to a method for making a magnetic recording/reading
head. It can be applied especially to the making of multiple-track heads
for the reading of all types of media such as magnetic disks, magnetic
tapes and magnetic cards, in all fields covering all types of equipment
such as video recorders, computer peripherals, data recorders for space
vehicles, etc.
The writing and/or reading of a large number of tracks very close to one
another, for example tracks arranged in parallel on a magnetic tape at a
pitch of 10 .mu.m, requires a magnetic head having elementary heads
compatible with an information density of this type.
The French patent application No. 2 630 853 describes the organization of a
matrix head adapted to such an application. The French patent 2 648 940
describes various methods of making such a head.
However, there is a problem of the integration of the coils of the magnetic
heads and of the connection of these coils to the control circuits.
The invention proposes the making of an integrated head with its coils and
also the integration of the control circuits. This removes the drawbacks
of the prior art. The resulting component is potentially inexpensive and
provides for a greater density of gaps in a matrix organization of
magnetic heads.
According to the invention, the integrated head takes the form of a
component combining control logic, power transistors, multiple-turn coils
and magnetic circuits.
SUMMARY OF THE INVENTION
The invention therefore relates to a method for the making of a magnetic
recording/reading head comprising the following steps:
the making of magnetic excitation wires on or in a first face of a
substrate comprising this first face and a second face opposite the first
face;
the making, on the first or second face of the substrate, of at least two
magnetic poles separated by a gap;
the drilling of holes through the substrate from the face opposite the one
bearing the magnetic poles, each ending in such a way that there is
magnetic coupling between the bottom of the hole and the pole;
the deposition of a layer of material with high magnetic permeability in
the holes and in the zones of the substrate located between the holes.
The invention also relates to a magnetic recording/reading head comprising
a non-magnetic substrate having, on one face, at least one magnetic
excitation conductor and, on this face or on the opposite face, two
magnetic poles separated by a gap as well as an element made of a material
with high magnetic permeability having a U-shape, with the arms of this U
being substantially perpendicular to the face bearing the magnetic poles
and with the ends of the arms being each magnetically coupled with a
magnetic pole, said element and said poles forming a magnetic circuit that
surrounds the conductor, wherein the substrate is made of a semiconductor
material in which the control circuits to which the conductor is connected
are implanted.
BRIEF DESCRIPTION OF THE DRAWINGS
The different objects and features of the invention shall appear more
clearly from the following description, and from the appended figures, of
which:
FIG. 1 shows a general exemplary embodiment according to the invention;
FIG. 2 shows a detailed example of a magnetic head according to the
invention;
FIGS. 3a to 3e show a method for the making of a magnetic head according to
the invention;
FIGS. 4a to 4e show a variant of the method of manufacture according to the
invention;
FIG. 5 shows a magnetic head and a method of manufacture according to which
magnetic poles are not directly on the substrate plate;
FIG. 6 shows a variant of the method of manufacture of FIG. 5;
FIG. 7 shows an application of the invention to the making of matrix
magnetic head;
FIGS. 8 to 14 show different modes of coils of a matrix magnetic head.
MORE DETAILED DESCRIPTION
According to the invention, the control logic circuits, the supply
transistors and the coils are made on a substrate of semiconductor
material (silicon) by using a technology that is now tested and widely
used on an industrial scale such as, for example, a technology using
complementary MOS transistors and a double level of metallization. FIG. 1
gives a schematic view of such a circuit of the kind that can be obtained
on wafers in the semiconductor industry. It will be noted that the
connections are positioned on the top and bottom edges of the chip so as
to free the right-hand and left-hand edges for the running of the tape.
The control transistors have a resistance well below that of the coils so
that the currents are determined by the impedance of said coils. It
follows therefrom that the heat dissipation zone is that of the coils.
FIG. 2 shows an example of a schematic sectional view in the zone of the
coils. It shows a magnetic circuit with a gap imbricated in a coil.
It has a substrate 1 bearing, on one of its faces 10, magnetic excitation
conductors 2 or coil wires. The substrate 1 is, for example, made of
semiconductor material (silicon for example) and control circuits 7, 7'
are implanted in the substrate. The circuits 7, 7' are therefore
semiconductor circuits and contain power transistor circuits that can be
used to supply the connection wires with current. They are then connected
by means known in the prior art to the excitation wires 2. The circuits 7,
7' may also contain logic control circuits receiving commands from the
exterior and controlling the power supply circuits of the excitation
wires.
Above the coils there are positioned magnetic poles 3, 3' separated by a
gap 30. A layer of insulator material 13 may be provided above the
excitation wires 2. This layer, whose surface is plane and slightly
curved, enables the poles 3, 3' to be received easily and to be insulated
from the excitation wires 2. The poles 3, 3' are made advantageously
according to the method for the manufacture of thin layers as described in
the French patent application No. 2 605 783.
Holes 12 and 12' go through the substrate 1 and the layer 13 and contain a
material with high magnetic permeability 4 in such a way that this
material is in contact or almost in contact with the poles 3, 3' so as to
be magnetically coupled with the poles 3, 3'. The layer 4 therefore
magnetically couples the poles 3 and 3' to each other.
Finally, a supporting plate 6 which is preferably rigid is fixed to the
face 11 of the substrate 1 with, for example, bonder 5. Advantageously,
the plate 6 is made of a material that is a good conductor of heat, for
example silicon, to enable the cooling of the circuits.
According to the exemplary embodiment of FIG. 2, the excitation wires 2 and
the circuits 7, 7' are positioned on the face 10 of the substrate but in
another embodiment they could be on the face 11.
Referring to FIGS. 3a to 3e, a description shall now be given of a method
for making a magnetic head according to the invention.
In a first step (FIG. 3a), control circuits 7, 7' and excitation wires 2
are made on the surface 10 of a substrate 1. In the case of an embodiment
using semiconductors, the control circuits 7, 7' are implanted in the
substrate and the excitation wires 2 are made on the surface of the
substrate. The excitation wires 2 are electrically connected to the
control circuits 7, 7'. The face 10 and the excitation wires are covered
with an insulator layer 13. This layer is preferably flattened or slightly
curved (in the case of applications for the reading of magnetic tapes).
In a second step, the magnetic poles 3, 3' separated by a gap are made on
the layer 13. According to a thin-layer manufacturing method, the magnetic
pole 3 is made on the face 10 and then a layer of non-magnetic material 30
is made on this pole.
This non-magnetic layer 30 has a thickness smaller than that of the pole 3.
A layer of magnetic material designed to form the pole 3 is then made on
the unit. Then, this magnetic layer and the non-magnetic layer 30 are
machined above the pole 3 so as to bring out this pole 3. Thus the
structure of FIG. 3b is obtained.
According to the exemplary embodiment of FIG. 3b, the layer of non-magnetic
material 30 located between the poles 3' and the face 10 has been kept
but, according to another embodiment, it could be eliminated.
During a third step (FIG. 3c), holes 12, 12' are drilled in the substrate 1
from the face 11. The hole 12 preferably reaches the pole 3. The hole 12'
reaches the layer 30 or the pole 3'. The holes 12 and 12' may also be
holes that do not lead into the substrate 1 or the layer 13. It is enough
then that there should be a magnetic coupling between the poles 3, 3' and
the holes 12, 12' respectively.
In a fourth step (FIG. 3d), a material with high magnetic permeability 4 is
then deposited in the holes 12, 12' and on the zone of the substrate 1
located between the holes. This material 4 is aimed at obtaining the
magnetic coupling of the poles 3 and 3' and forming the element that
closes the magnetic circuit of the magnetic head.
In this state, the magnetic head according to the invention is made.
In a fifth step (FIG. 3e) the face 11 of substrate may be fixed to a
supporting plate 6 whose role is to make the unit rigid as well as
possibly to act as a cooling unit.
For example, the thickness of the substrate 1 may be equal to about a
hundred micrometers while that of the pole 3 may be equal to about ten
micrometers while the non-magnetic layer 30 is some micrometers thick.
The materials used will be for example:
substrate=silicon
poles 3, 3'=sendust (alloy of iron, tin and aluminium)
layer of magnetic material 4=permalloy.
FIGS. 4a to 4e show an alternative to the method described here above.
In FIG. 4a, during the first step, the excitation wires and circuits 7, 7'
are made on the face 11 of the substrate.
In the second step (FIG. 4b), the magnetic poles 3, 3' are made on the face
10.
The holes 12, 12' are made during the third step (FIG. 4c) as here above.
Then, the magnetic material 4 is deposited in the holes 12, 12' as above
(FIG. 4d). Finally, a supporting element 6 is attached to the unit.
There is thus obtained a structure (FIG. 4e) which differs from that of
FIG. 3e by the fact that the excitation wires and the control circuits 7,
7' are made on the face 11 instead of on the face 10.
The difficulty with this type of completely integrated technology is the
compatibility of the operations for processing the magnetic head and the
silicon circuits. There is a risk of destroying the logic transistors and
the control transistors during the operations for annealing the poles.
This is why an alternative method of manufacture shall now be described.
This alternative method is illustrated in FIG. 5.
A composite plate 9 made of non-magnetic material 90 and of magnetic
material 91 is made separately. The non-magnetic material 90 is, for
example, glass and the magnetic material 91 is ferrite. The magnetic poles
3, 3' are made on a face 92 above magnetic zones 91 so that each of them
is magnetically coupled to the face 93 of the plate 9.
During the second step described here above, this face is then fixed by
bonding, for example, to the face 10 of the substrate.
The substrate 1 is then thinned out on the face 11 side and then holes are
drilled in the substrate 1 before the electrodeposition of permalloy as
here above. A supporting plate 6 of silicon or heat conductor may then be
bonded to make the unit rigid.
Other variants may give the final result. In particular, the U-shaped
permalloy structure may be obtained on the active faces of the chips
(after the making of blind holes by chemical corrosion) and then the heat
conductor is bonded to this active face or thinned out by the rear face up
to the permalloy and the unit is bonded to the glass-ferrite composite
material.
According to another variant shown in FIG. 6, instead of using a plate 9 of
composite material, a wafer 8 of homogeneous and non-magnetic material
such as silicon is used. The magnetic poles 3, 3' are made on this wafer.
Then this wafer is thinned out. Then, as here above, this wafer 8 is
attached to the substrate plate 1 bearing the excitation wires 2 and the
control circuits. The plate 1 is thinned out. Then, the holes 12 and 12'
are made through the substrate 1 and through the wafer 8.
The magnetic material 4 deposited in the holes 12, 12' enables the
constituting of the magnetic circuits coupling the two magnetic poles 3
and 3'.
Various alternative ways of making the magnetic closing circuit are
possible. The first silicon substrate may be drilled with its blind holes
(leading to the poles) before the bonding of the second substrate. These
same blind holes may be filled with permalloy before bonding. This brings
us to the variants explained in the above paragraph.
This embodiment is advantageous for two reasons:
the two silicon substrates 1 and 8 may have the same dimensions;
the density of the gaps may be greater than in the previous approach
because there is no longer any glass-ferrite composite material used.
The coils may be made in two levels of metallization with the possibility
of connecting these two levels by cross-connections that go through the
substrate 1 and even through the supporting plate 6.
The invention can be applied to the making of a set of matrix heads as
shown in FIG. 7 and described in the French patent application No. 2 630
853.
In a set of heads such as this, the heads are organized in rows and
columns. A head such as T1 has two poles 3, 3' separated by a gap 30, each
located on a magnetic pad PL1 connected to a layer or to a plate of
magnetic material 1. Magnetic excitation conductors or row coils L1 enable
the induction of a magnetic flux in the magnetic circuits of a row of
magnetic heads. Other magnetic excitation conductors or column coils C1
enable the induction of a magnetic flux in the magnetic circuits of a
column of magnetic heads. A magnetic head located at the intersection of a
row coil and a column coil is excited.
According to the invention, the coil conductors are not housed in grooves.
They are on the surface of the substrate 1. The working of the magnetic
heads is, however, the same. Their mode of coiling determines the pads
PL1.
FIGS. 8 to 14 show different modes of coils made possible by the method of
the invention.
FIG. 8 shows a matrix head in which each magnetic head has its own two
poles. Each row of magnetic heads has a row coil, D1 for example, that is
individually coiled around the poles D1 of a row. Each column of magnetic
heads has a column coil S1 that is coiled around all the poles D1 to D5 of
a column together. Such an arrangement enables the reduction of all
cross-talk between magnetic heads owing to the fact that there is no
common pole between neighboring heads. A mode of coiling such as this also
enables the reduction of the inductance.
FIG. 9 shows a matrix head in which a magnetic pole is common to two heads.
A row coil D1 is coiled around the poles of a row. For each column, there
are two coils such as S3 and S4 coiled around the poles of a column
alternately.
FIG. 10 shows a mode of coiling in which it is the column coils that are
each common to a column of poles and in which there are two row coils
coiled around the poles of a row alternately.
FIG. 11 shows a mode of coiling similar to that of FIG. 9, but the magnetic
heads are positioned in a zigzag arrangement and connect the magnetic
poles diagonally.
FIG. 12 shows a mode of coiling similar to that of FIG. 11 but wherein the
pads and poles are square-shaped. They are positioned at 45.degree. with
respect to the direction of the rows and columns.
FIG. 13 shows a mode of coiling in which the pads and poles positioned at
45.degree. (as in FIG. 12) have row coils and column coils coiled around
them individually.
FIG. 14 shows a mode of coiling in which there are two coils per row D3, D4
for example, coiled around the poles of a row alternately as well as two
coils per column S1 and S2 for example, coiled around the poles of a
column alternately.
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